Do I really need an MRI for my aching back or knees?


One of my professors in medical school had a saying that has stuck with me for all these years: Don’t reach past a patient to treat a test result.

What he meant was, even though tests can show us some abnormalities, those specific abnormalities may not be necessary to treat.  In fact, proving the existence of the abnormality doesn’t change our treatment whatsoever.

A good example of this is doing MRIs for a disc injury in the back.

First of all, MRI stands for Magnetic Resonance Imaging.  A powerful magnet is used to take pictures of the back, in the same way, an x-ray does.  By rotating the magnetic beam around the patient, we can use a computer to reconstruct images that look like “slices” through the body, giving us the beautiful detail of the various structures in the back.

Healthy and secure living

The symptoms and signs of a disc injury, or “bulging disc”, are generally clear on examination by the physician, and so usually we can direct treatment based solely on asking questions and examining the patient.  Disc injuries are treated with therapy, acupuncture, medications and modifications to activity.  The vast majority of people with a disc injury will get better without surgery.   Disc injuries are also extremely common.

So imagine, if we took MRI pictures of everyone with a disc injury, we’d have thousands of people doing tests that in the end would not change how we treat them.

Despite wait times initiatives, the time it takes to get an MRI in Canada is still in the order of weeks, not days or hours.  Clearly, the more we can do to reduce the number of unnecessary MRIs that we do, the more likely it is that someone with a pressing need for an MRI will get one sooner.

Another common area to do MRIs is for knee injuries.  A study last year published in the Clinical Journal of Sports Medicine showed that the clinical examination is as accurate as MRI in determining if you have a knee cartilage injury that requires surgery.  Another study published in the journal Arthroscopy in 2004 showed that MRI is actually slightly less accurate than the clinical examination for cartilage injuries or complete tears of the anterior cruciate ligament (ACL).  Furthermore, just as with the back, there are many knee cartilage and ligament injuries that don’t require surgery.  Many will settle down on their own with rehabilitation and time.

I hear this all the time from patients: “Well, when my friend had a knee injury, he got an MRI, and that’s what I want.”  But again, if it isn’t going to change management, then it’s only going to be a waste of time and resources.

No doctor is right all the time, although those people who diagnose and treat these types of problems day in and day out have a better chance at being right.  So there are times when initial impressions of an injury can be misleading, and an MRI may be decided on later in the course of treatment.  But I believe both physicians and patients should be thinking about the necessity of testing before putting patients into the ever-growing queues for MRIs.